1. Technical Field
The present invention relates to an optical information reproducing apparatus and an optical information recording apparatus using holography.
2. Related Art
In recording information onto a recording medium using holography, an information beam carrying image information and a recording-specific reference beam overlap each other in the recording medium and an interference pattern generated thereby is written onto the recording medium. For reproducing the recorded information, a reproducing-specific reference beam is irradiated onto the recording medium so as to reproduce image information by diffraction in the interference pattern.
Volume holography has been developed for achieving high density optical recording and high data transmission rate. The volume holography is a method in which the interference patterns are written tree-dimensionally by actively utilizing the thickness direction of the recoding medium. Since the volume holography can employ a parallel signal processing operation for input and output of data, it is possible to basically enhance a data transmission rate in comparison with a compact disc (CD) and a digital versatile disc (DVD). In addition, it is possible to drastically enhance the recording density by using a multiplexing technique.
The recording medium can employ a disc-type medium such as a CD, a DVD and the like. The recording medium rotates about a fixed axis, and a plurality of tracks is formed from the center thereof.
A holographic optical information processing apparatus includes an optical pickup to drive an objective lens through rotating the recording medium. The optical pickup performs a focus servo and tracking servo by driving the objective lens.
U.S. Pat. No. 6,807,671 discloses an optical pickup having a light source, a spatial light modulator and an objective lens. The optical pickup is driven to record optical information in the recording medium or reproduce the optical information from the recording medium.
Generally, an optical pickup moves to a predetermined recording position or reproducing position of the recording medium so as to process the optical information by track. When operating the optical pick, a vibration is externally or internally caused between the objective lens and an other optical system. Even when the vibration of the optical pick is smaller in comparison with that of the other part of the optical information processing apparatuses, the vibration has a large influence on recording/reproducing the optical information. At the time of recording the optical information, the small vibration of the optical system in the optical pickup can causes a large variation in interference pattern, whereby the optical information cannot be accurately recorded. At the time of reproducing the optical information, when the reproducing-specific reference beam is shifted, the interference pattern can be changed, whereby the optical information cannot be accurately reproduced.
The optical pickup of the holographic optical information processing apparatus includes relatively heavy and large devices such as a spatial light modulator and a charge-coupled device, in addition to an optical system. Accordingly, it is not easy to reduce the vibration caused by the operation of the optical pickup and to improve the data transmission rate.